Data communications system, optical line terminal, and baseband unit

ABSTRACT

This application discloses a bandwidth allocation method, an optical line terminal (OLT), an optical network unit (ONU), and a system, where the method includes receiving a bandwidth request from each ONU, where the ONU includes an ONU1, generating a bandwidth map (BWMap) message according to bandwidth requested by the ONU and bandwidth configured for the ONU, where the BWMap message includes a first allocation identifier (Alloc-ID1), a first time corresponding to the Alloc-ID1, a second allocation identifier (Alloc-ID2), and a second time corresponding to the Alloc-ID2, and both the Alloc-ID1 and the Alloc-ID2 are allocated to the ONU1 for use, and sending the BWMap message to each ONU. Therefore, a problem that a transmission delay does not satisfy a requirement when a passive optical network (PON) system is applied to mobile backhaul is resolved, a data transmission rate and data transmission efficiency are improved, and user satisfaction is improved.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/862,285, filed on Jan. 4, 2018, which is a continuation ofInternational Application No. PCT/CN2016/113857, filed on Dec. 30, 2016.All of the afore-mentioned patent applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

This application relates to the optical communications field, and inparticular, to a data communications system, an optical line terminal(OLT), and a baseband unit (BBU).

BACKGROUND

A passive optical network (PON) is a point-to-multipoint networktopology structure, and generally includes an OLT that is located at acentral office (CO), multiple optical network units (ONUs) that arelocated at a user end, and an optical distribution network (ODN) that islocated between the OLT and the multiple ONUs.

In a PON system, dynamic bandwidth assignment (DBA) is a mechanism inwhich upstream bandwidth can be dynamically allocated within a timeinterval at a microsecond (μs) or millisecond (ms) level. In an existingPON system, an OLT delivers, by means of broadcasting, a bandwidth map(BWMap) message according to requested bandwidth reported by each ONUsuch that the ONU transmits, using the BWMap message, data within a timeallocated by the OLT. However, because in the current bandwidthallocation mechanism, an average delay generated from sending data usingan upstream port of the ONU to receiving the data using a PON port ofthe OLT is at least 300 μs, and even 1 to 4 ms, for a mobile backhaulscenario to which fifth generation (5G) is applied, due to a real timetransmission requirement of user data, a system stipulates that thedelay generated in a period from sending the data using the upstreamport of the ONU to receiving the data using the port of the OLT iswithin 20 μs. In a current DBA mechanism, a delay in a mobile bearingscenario cannot satisfy a delay performance requirement of servicetransmission.

SUMMARY

To resolve a problem that a transmission delay does not satisfy arequirement when a PON system is applied to mobile backhaul, and toimprove a data transmission rate and transmission efficiency by reducingthe transmission delay of the PON system, embodiments of the presentdisclosure provide the following technical solutions.

In a first design solution, a bandwidth allocation method is provided,and the method includes receiving a bandwidth request sent by each ONUs,where the ONU includes a first ONU (ONU1), generating a BWMap messageaccording to bandwidth requested by the ONU and bandwidth configured forthe ONU, where the BWMap message includes a first allocation identifier(Alloc-ID1), a first time corresponding to the Alloc-ID1, a secondallocation identifier (Alloc-ID2), and a second time corresponding tothe Alloc-ID2, and both the Alloc-ID1 and the Alloc-ID2 are allocated tothe ONU1 for use, and sending the BWMap message to each ONU.

In this design solution, after such design, bandwidth authorization maybe allocated to video data of the ONU1 twice in one period in order totransmit the video data. One transmission period is generally 125 μs.That is, within the 125 μs, the video data may be transmitted twice. Ifone period is 125 μs, a transmission time corresponding to eachtransmission container (T-CONT) is 125/6 that is approximately 21 μs,that is, a time interval between transmitting the video data for a firsttime and transmitting the video data for a next time is 63 μs. However,in an existing DBA transmission mechanism, if the ONU1 transmits thevideo data only once within 125 μs, a time interval between transmittingthe video data for a current time and transmitting the video data for anext time is 125 μs, and if the ONU1 misses this time of datatransmission, the ONU1 needs to wait for 125 μs to perform transmissionfor a second time. It can be learned that, according to such improvementon a BWMap message format in this embodiment of this application, notonly a service flow transmission interval of each ONU can be shortened,but also a transmission delay of the ONU is greatly reduced. It can belearned from an experiment that an average transmission delay of the ONUcan be reduced to within 20 μs such that a problem that a transmissiondelay does not satisfy a requirement when a PON system is applied tomobile backhaul is resolved, a data transmission rate and datatransmission efficiency are improved, and user satisfaction is improved.

Based on the foregoing design solution, in a possible design, the BWMapmessage further includes a third allocation identifier (Alloc-ID3) and athird time corresponding to the Alloc-ID3, the Alloc-ID3 is used toidentify a second ONU (ONU2), and the third time is used to be allocatedto the ONU2 for use.

Based on the foregoing design solution, in another possible design, thefirst time includes a start time 1 and an end time 1, the second timeincludes a start time 2 and an end time 2, the start time 1 is used toindicate a byte at which the ONU1 starts to transmit a first datastream, the end time 1 is used to indicate a byte at which the ONU1 endstransmission of the first data stream, the start time 2 is used toindicate a byte at which the ONU1 starts to transmit a second datastream, the end time 2 is used to indicate a byte at which the ONU1 endstransmission of the second data stream, and the first data stream andthe second data stream carry service flows of a same type, or the firstdata stream and the second data stream carry service flows of differenttypes.

Based on the foregoing design solution, in another possible design, alocation of the Alloc-ID1 relative to the Alloc-ID2 is fixed in a BWMapmessage in each period.

In a second design solution, a bandwidth allocation method is provided,and the method includes sending a BWMap request to an OLT to request theOLT to allocate bandwidth, and receiving a BWMap message returned by theOLT, where the BWMap message includes an Alloc-ID1, a first timecorresponding to the Alloc-ID1, an Alloc-ID2, and a second timecorresponding to the Alloc-ID2, and both the Alloc-ID1 and the Alloc-ID2are allocated to the ONU1.

In this design solution, after such design, bandwidth authorization maybe allocated to video data of the ONU1 twice in one period in order totransmit the video data. One transmission period is generally 125 μs.That is, within the 125 μs seconds, the video data may be transmittedtwice. If one period is 125 μs, a transmission time corresponding toeach T-CONT is 125/6 that is approximately 21 μs, that is, a timeinterval between transmitting the video data for a first time andtransmitting the video data for a next time is 63 μs. However, in anexisting DBA transmission mechanism, if the ONU1 transmits the videodata only once within 125 μs, a time interval between transmitting thevideo data for a current time and transmitting the video data for a nexttime is 125 μs, and if the ONU1 misses this time of data transmission,the ONU1 needs to wait for 125 μs to perform transmission for a secondtime. It can be learned that, according to such improvement on a BWMapmessage format in this embodiment of this application, not only aservice flow transmission interval of each ONU can be shortened, butalso a transmission delay of the ONU is greatly reduced. It can belearned from an experiment that an average transmission delay of the ONUcan be reduced to within 20 μs such that a problem that a transmissiondelay does not satisfy a requirement when a PON system is applied tomobile backhaul is resolved, a data transmission rate and datatransmission efficiency are improved, and user satisfaction is improved.

Based on the foregoing design solution, in a possible design, the methodfurther includes obtaining, according to an Alloc-ID of the ONU1, afirst time and a second time corresponding to the ONU1, and transmittingfirst data according to the obtained first time, and transmitting seconddata according to the second time.

Based on the foregoing design solution, in another possible design, theBWMap message further includes an Alloc-ID3 and a third timecorresponding to the Alloc-ID3, the Alloc-ID3 is used to identify anONU2, and the third time is used to be allocated to the ONU2 for use.

Based on the foregoing design solution, in a possible design, the firsttime includes a start time 1 and an end time 1, the second time includesa start time 2 and an end time 2, the start time 1 is used to indicate abyte at which the ONU1 starts to transmit a first data stream, the endtime 1 is used to indicate a byte at which the ONU1 ends transmission ofthe first data stream, the start time 2 is used to indicate a byte atwhich the ONU1 starts to transmit a second data stream, the end time 2is used to indicate a byte at which the ONU1 ends transmission of thesecond data stream, and the first data stream and the second data streamcarry service flows of a same type, or the first data stream and thesecond data stream carry service flows of different types.

Based on the foregoing design solution, in another possible design, alocation of the Alloc-ID1 relative to the Alloc-ID2 is fixed in a BWMapmessage in each period.

In a third design solution, an OLT is provided, and the OLT includes atransceiver configured to receive a bandwidth request sent by each ONU,where the ONU includes an ONU1, and send a BWMap message to each ONU,and a processor configured to generate the BWMap message according tobandwidth requested by the ONU and bandwidth configured for the ONU,where the BWMap message includes an Alloc-ID1, a first timecorresponding to the Alloc-ID1, an Alloc-ID2, and a second timecorresponding to the Alloc-ID2, and both the Alloc-ID1 and the Alloc-ID2are allocated to the ONU1 for use.

In this design solution, after such design, bandwidth authorization maybe allocated to video data of the ONU1 twice in one period in order totransmit the video data. One transmission period is generally 125 μs.That is, within the 125 μs seconds, the video data may be transmittedtwice. If one period is 125 μs, a transmission time corresponding toeach T-CONT is 125/6 that is approximately 21 μs, that is, a timeinterval between transmitting the video data for a first time andtransmitting the video data for a next time is 63 μs. However, in anexisting DBA transmission mechanism, if the ONU1 transmits the videodata only once within 125 μs, a time interval between transmitting thevideo data for a current time and transmitting the video data for a nexttime is 125 μs, and if the ONU1 misses this time of data transmission,the ONU1 needs to wait for 125 μs to perform transmission for a secondtime. It can be learned that, according to such improvement on a BWMapmessage format in this embodiment of this application, not only aservice flow transmission interval of each ONU can be shortened, butalso a transmission delay of the ONU is greatly reduced. It can belearned from an experiment that an average transmission delay of the ONUcan be reduced to within 20 μs such that a problem that a transmissiondelay does not satisfy a requirement when a PON system is applied tomobile backhaul is resolved, a data transmission rate and datatransmission efficiency are improved, and user satisfaction is improved.

Based on the third design solution, in a possible design, the BWMapmessage further includes an Alloc-ID3 and a third time corresponding tothe Alloc-ID3, the Alloc-ID3 is used to identify an ONU2, and the thirdtime is used to be allocated to the ONU2 for use.

Based on the third design solution, in another possible design, thefirst time includes a start time 1 and an end time 1, the second timeincludes a start time 2 and an end time 2, the start time 1 is used toindicate a byte at which the ONU1 starts to transmit a first datastream, the end time 1 is used to indicate a byte at which the ONU1 endstransmission of the first data stream, the start time 2 is used toindicate a byte at which the ONU1 starts to transmit a second datastream, the end time 2 is used to indicate a byte at which the ONU1 endstransmission of the second data stream, and the first data stream andthe second data stream carry service flows of a same type, or the firstdata stream and the second data stream carry service flows of differenttypes.

Based on the third design solution, in another possible design, alocation of the Alloc-ID1 relative to the Alloc-ID2 is fixed in a BWMapmessage in each period.

In this design solution, after such design, bandwidth authorization maybe allocated to video data of the ONU1 twice in one period in order totransmit the video data. One transmission period is generally 125 μs.That is, within the 125 μs seconds, the video data may be transmittedtwice. If one period is 125 μs, a transmission time corresponding toeach T-CONT is 125/6 that is approximately 21 μs, that is, a timeinterval between transmitting the video data for a first time andtransmitting the video data for a next time is 63 μs. However, in anexisting DBA transmission mechanism, if the ONU1 transmits the videodata only once within 125 μs, a time interval between transmitting thevideo data for a current time and transmitting the video data for a nexttime is 125 μs, and if the ONU1 misses this time of data transmission,the ONU1 needs to wait for 125 μs to perform transmission for a secondtime. It can be learned that, according to such improvement on a BWMapmessage format in this embodiment of this application, not only aservice flow transmission interval of each ONU can be shortened, butalso a transmission delay of the ONU is greatly reduced. It can belearned from an experiment that an average transmission delay of the ONUcan be reduced to within 20 μs such that a problem that a transmissiondelay does not satisfy a requirement when a PON system is applied tomobile backhaul is resolved, a data transmission rate and datatransmission efficiency are improved, and user satisfaction is improved.

In a fourth design solution, an ONU is provided, and the ONU includes atransmitter configured to send a bandwidth request to an OLT, and areceiver configured to receive a BWMap message returned by the OLT,where the BWMap message includes an Alloc-ID1, a first timecorresponding to the Alloc-ID1, an Alloc-ID2, and a second timecorresponding to the Alloc-ID2, and both the Alloc-ID1 and the Alloc-ID2are allocated to the ONU1.

Based on the fourth design solution, a possible implementation isprovided, where the ONU further includes a processor configured toobtain, according to an Alloc-ID of the ONU1, a first time and a secondtime corresponding to the ONU1, and instruct the transmitter to transmitdata in the first time and the second time, and the transmitter isfurther configured to transmit first data according to the obtainedfirst time, and transmit second data according to the second time.

Based on the fourth design solution, another possible implementation isprovided, where the BWMap message further includes an Alloc-ID3 and athird time corresponding to the Alloc-ID3, the Alloc-ID3 is used toidentify an ONU2, and the third time is used to be allocated to the ONU2for use.

Based on the fourth design solution, a third possible implementation isprovided, where the first time includes a start time 1 and an end time1, the second time includes a start time 2 and an end time 2, the starttime 1 is used to indicate a byte at which the ONU1 starts to transmit afirst data stream, the end time 1 is used to indicate a byte at whichthe ONU1 ends transmission of the first data stream, the start time 2 isused to indicate a byte at which the ONU1 starts to transmit a seconddata stream, the end time 2 is used to indicate a byte at which the ONU1ends transmission of the second data stream, and the first data streamand the second data stream carry service flows of a same type, or thefirst data stream and the second data stream carry service flows ofdifferent types.

Based on the fourth design solution, a fourth possible implementation isprovided, where a location of the Alloc-ID1 relative to the Alloc-ID2 isfixed in a BWMap message in each period.

In this design solution, after such design, bandwidth authorization maybe allocated to video data of the ONU1 twice in one period in order totransmit the video data. One transmission period is generally 125 μs.That is, within the 125 μs seconds, the video data may be transmittedtwice. If one period is 125 μs, a transmission time corresponding toeach T-CONT is 125/6 that is approximately 21 μs, that is, a timeinterval between transmitting the video data for a first time andtransmitting the video data for a next time is 63 μs. However, in anexisting DBA transmission mechanism, if the ONU1 transmits the videodata only once within 125 μs, a time interval between transmitting thevideo data for a current time and transmitting the video data for a nexttime is 125 μs, and if the ONU1 misses this time of data transmission,the ONU1 needs to wait for 125 μs to perform transmission for a secondtime. It can be learned that, according to such improvement on a BWMapmessage format in this embodiment of this application, not only aservice flow transmission interval of each ONU can be shortened, butalso a transmission delay of the ONU is greatly reduced. It can belearned from an experiment that an average transmission delay of the ONUcan be reduced to within 20 μs such that a problem that a transmissiondelay does not satisfy a requirement when a PON system is applied tomobile backhaul is resolved, a data transmission rate and datatransmission efficiency are improved, and user satisfaction is improved.

In a fifth design solution, a PON system is provided, including an OLTand an ONU. The OLT is connected to the ONU using an ODN, the OLTincludes the OLT related to the foregoing third design solution, and theONU includes the ONU according to the foregoing design solution.

In this design solution, after such design, bandwidth authorization maybe allocated to video data of the ONU1 twice in one period in order totransmit the video data. One transmission period is generally 125 μs.That is, within the 125 μs seconds, the video data may be transmittedtwice. If one period is 125 μs, a transmission time corresponding toeach T-CONT is 125/6 that is approximately 21 μs, that is, a timeinterval between transmitting the video data for a first time andtransmitting the video data for a next time is 63 μs. However, in anexisting DBA transmission mechanism, if the ONU1 transmits the videodata only once within 125 μs, a time interval between transmitting thevideo data for a current time and transmitting the video data for a nexttime is 125 μs, and if the ONU1 misses this time of data transmission,the ONU1 needs to wait for 125 μs to perform transmission for a secondtime. It can be learned that, according to such improvement on a BWMapmessage format in this embodiment of this application, not only aservice flow transmission interval of each ONU can be shortened, butalso a transmission delay of the ONU is greatly reduced. It can belearned from an experiment that an average transmission delay of the ONUcan be reduced to within 20 μs such that a problem that a transmissiondelay does not satisfy a requirement when a PON system is applied tomobile backhaul is resolved, a data transmission rate and datatransmission efficiency are improved, and user satisfaction is improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a system architecture diagram of a data communications systemaccording to an embodiment of this application;

FIG. 2 is a schematic flowchart of a bandwidth allocation methodaccording to an embodiment of this application;

FIG. 3 shows a BWMap message format according to an embodiment of thisapplication;

FIG. 4 is a diagram of an allocation period corresponding to a BWMapmessage according to an embodiment of this application;

FIG. 5A and FIG. 5B show a BWMap message format according to anembodiment of this application;

FIG. 6 is a diagram of an allocation period corresponding to a BWMapmessage according to an embodiment of this application;

FIG. 7A and FIG. 7B show another BWMap message format according to anembodiment of this application;

FIG. 8 is a schematic structural diagram of an OLT according to anembodiment of this application;

FIG. 9 is a schematic structural diagram of an ONU according to anembodiment of this application; and

FIG. 10 is a schematic structural diagram of data communications deviceaccording to an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of thisapplication clearer, the following further describes the implementationsof this application in detail with reference to the accompanyingdrawings.

“Multiple” described in this application means two or more. The term“and/or” describes an association relationship of associated objects andindicates that three relationships may exist. For example, A and/or Bmay represent the three cases that only A exists, both A and B exist,and only B exists. The character “/” generally indicates an “or”relationship between the associated objects.

Referring to FIG. 1 , a PON system 100 includes at least one OLT 110,multiple ONUs 120, and an ODN 130. The OLT 110 is connected to themultiple ONUs 120 in a point-to-multipoint manner using the ODN 130. TheOLT 110 may communicate with the ONU 120 using a time divisionmultiplexing (TDM) mechanism, a wavelength division multiplexing (WDM)mechanism, or a TDM/WDM hybrid mechanism. A direction from the OLT 110to the ONU 120 is defined as a downstream direction, and a directionfrom the ONU 120 to the OLT 110 is an upstream direction.

The PON system 100 may be a communications network that does not needany active component to distribute data between the OLT 110 and the ONU120. In a specific embodiment, the data may be distributed between theOLT 110 and the ONU 120 using a passive optical component (such as anoptical splitter) in the ODN 130. The PON system 100 may be anasynchronous transfer mode (ATM) PON system or a broadband PON (BPON)system defined in the International Telecommunication UnionTelecommunication Standardization Sector (ITU-T) G.983 standard, agigabit PON (GPON) system defined in the ITU-T G.984 series ofstandards, an Ethernet PON (EPON) system defined in the Institute ofElectrical and Electronics Engineers IEEE 802.3ah standard, a WDM PONsystem, or a next-generation (NGA) PON system such as an XGPON systemdefined in the ITU-T G.987 series of standards, a 10 gigabit (10G) EPONsystem defined in the IEEE 802.3av standard, or a TDM/WDM hybrid PONsystem. Various PON systems defined by the foregoing standards areincorporated in this application document by reference in theirentireties.

The OLT 110 is usually located at a central location (such as a CO), andmay manage all the multiple ONUs 120. The OLT 110 may be used as amedium between the ONU 120 and an upper-layer network (not shown), usedata received from the upper-layer network as downstream data, forwardthe downstream data to the ONUs 120, and forward upstream data receivedfrom the ONU 120 to the upper-layer network. Specific structureconfiguration of the OLT 110 may vary with a specific type of the PON100. In an embodiment, the OLT 110 may include an optical transceivercomponent 200 and a data processing module (not shown). The opticaltransceiver component 200 may convert downstream data processed by thedata processing module into a downstream optical signal, send thedownstream optical signal to the ONU 120 using the ODN 130, receive anupstream optical signal sent by the ONU 120 using the ODN 130, convertthe upstream optical signal into an electrical signal, and provide theelectrical signal for the data processing module for processing.

The ONUs 120 may be disposed at user side locations (such as customerresidences) in a distributed manner. The ONU 120 may be a network deviceconfigured to communicate with the OLT 110 and a user. Further, the ONU120 may be used as a medium between the OLT 110 and the user. Forexample, the ONU 120 may forward downstream data received from the OLT110 to the user, and set data received from the user as upstream dataand forward the upstream data to the OLT 110. Specific structureconfiguration of the ONU 120 may vary with a specific type of the PON100. In an embodiment, the ONUs 120 may include an optical transceivercomponent 300. The optical transceiver component 300 is configured toreceive a downstream data signal sent by the OLT 110 using the ODN 130,and send an upstream data signal to the OLT 110 using the ODN 130. Itshould be understood that, in this application document, a structure ofthe ONU 120 is similar to that of the optical network terminal (ONT).Therefore, in a solution in this application document, the ONU and theONT may be interchanged.

The ODN 130 may be a data distribution system, and may include a fiber,an optical coupler, an optical multiplexer/demultiplexer, an opticalsplitter, and/or another device. In an embodiment, the fiber, theoptical coupler, the optical multiplexer/demultiplexer, the opticalsplitter, and/or the other device may be passive optical components.Further, the fiber, the optical coupler, the opticalmultiplexer/demultiplexer, the optical splitter, and/or the other devicemay be components that do not need to be supported by a power supplywhen data signals are distributed between the OLT 110 and the ONUs 120.In addition, in another embodiment, the ODN 130 may further include oneor more processing devices, such as an optical amplifier or a relaydevice. In a branch structure shown in FIG. 1 , the ODN 130 may befurther extended to the multiple ONUs 120 from the OLT 110, but may alsobe configured as any other point-to-multipoint structure.

The optical transceiver component 200 or 300 may be a pluggable opticaltransceiver component integrated with an optical signal transmitting andreceiving function, an optical-to-electrical conversion function, and anOptical Time Domain Reflectometer (OTDR) testing function. The opticaltransceiver component 200 of the OLT 110 is used as an example, and theoptical transceiver component 200 may include an optical transmittingmodule (not shown), an optical receiving module (not shown), and an OTDRtesting module (not shown). The optical transmitting module isconfigured to deliver a downstream data signal to the ONU 120 using theODN 130, modulate an OTDR testing signal to the downstream data signalaccording to the OTDR testing control signal provided by the OTDRtesting module when a fiber network and a PON device need to bedetected, and output the downstream data signal to the ODN 130. Theoptical receiving module is configured to receive an upstream datasignal that is from the ONU 120 and that is transmitted using the ODN130, convert the upstream data signal into an electrical signal by meansof optical-to-electrical conversion, and forward the electrical signalto a control module or a data processing module (not shown) of the OLT110 for processing.

It should be noted that, the PON system in FIG. 1 may be an EPON systemor a GPON system, or may be a 10G EPON system or a 100G EPON system, ormay be an 10G-PON (XG-PON) system, an XG-Symmetrical PON (XGS-PON)system, or a time and wavelength division multiplexed PON (TWDM-PON)system. This is not limited in this embodiment of this application.

Various bandwidth allocation methods described below are applicable tothe foregoing system in FIG. 1 .

Referring to FIG. 2 , FIG. 2 is a bandwidth allocation method, appliedto the foregoing system architecture in FIG. 1 .

The method includes the following steps.

Step S200: Each ONU sends a BWMap request to an OLT to request the OLTto allocate bandwidth, where the ONU includes an ONU1.

Step S202: The OLT receives the BWMap request sent by the ONU.

Step S204: The OLT generates a BWMap message according to bandwidthrequested by the ONU and bandwidth configured by the ONU, where theBWMap message includes an Alloc-ID1, a first time corresponding to theAlloc-ID1, an Alloc-ID2, and a second time corresponding to theAlloc-ID2, and both the Alloc-ID1 and the Alloc-ID2 are allocated to theONU1 for use.

Further, the first time includes a first start time start time 1 and afirst end time end time 1, the second time includes a second start timestart time 2 and a second end time end time 2, the start time 1 is usedto indicate a byte at which the ONU1 starts to transmit a first datastream, the end time 1 is used to indicate a byte at which the ONU1 endstransmission of the first data stream, the start time 2 is used toindicate a byte at which the ONU1 starts to transmit a second datastream, the second end time end time 2 is used to indicate a byte atwhich the ONU1 ends transmission of the second data stream, and thefirst data stream and the second data stream carry service flows of asame type, or the first data stream and the second data stream carryservice flows of different types.

Further, the BWMap message further includes an Alloc-ID3 and a thirdtime corresponding to the Alloc-ID3, the Alloc-ID3 is used to identify asecond ONU2, and the third time is used to be allocated to the ONU2 foruse.

A specific format of the BWMap message generated by the OLT is shown inFIG. 3 .

The BWMap message includes an Alloc-ID field, a start time (designatedas Start in FIG. 3 ) field, and an end time (designated as in FIG. 3 )field. The Alloc-ID field is used to identify a T-CONT allocated to eachONU, and the T-CONT is a container used to transmit data, and furtherindicates bytes of data streams that can be transmitted. The start timefield is used to indicate a time corresponding to a byte at which theT-CONT starts to carry data, and the end time field is used to indicatea time corresponding to a byte at which the T-CONT ends carrying of thedata. Because each ONU has a fixed transmission rate, and a transmissioncapacity corresponding to each ONU is also preconfigured, a timecorresponding to a start byte of the ONU and a time at which the ONUends sending of a to-be-transmitted byte may be learned according to thetransmission rate and a quantity of to-be-transmitted data bytes.Descriptions herein are consistent with descriptions of an ITU-T G.984.3BWMap field and an ITU-T G.987.3 BWMap field, and details are notdescribed herein.

As shown in FIG. 3 , that the OLT generates a BWMap message includingthe Alloc-ID1 is used to identify a T-CONT1 allocated to the ONU1, astart time 100 and an end time 300 indicate that the ONU1 starts to senddata at the 100^(th) byte and ends sending of the data at the 300^(th)byte, the T-CONT1 is used to carry a data capacity of 200 bytes, and theT-CONT1 is used to carry data of the ONU1. The Alloc-ID2 is used toidentify a T-CONT2 allocated to the ONU2, a start time 400 and an endtime 500 indicate that the ONU2 starts to send data at the 400^(th) byteand ends sending of the data at the 500^(th) byte, the T-CONT2 is usedto carry a data capacity of 100 bytes, and the T-CONT2 is used to carrydata of the ONU2. The Alloc-ID3 is used to identify a T-CONT3 allocatedto a third ONU (ONU3), a start time 520 and an end time 600 indicatethat the ONU3 starts to send data at the 520^(th) byte and ends sendingof the data at the 600^(th) byte, the T-CONT3 is used to carry a datacapacity of 80 bytes, and the T-CONT3 is used to carry data of the ONU3.Implementation of this BWMap message is different from implementation ofexisting BWMap message. The BWMap message in this period furtherincludes that the Alloc-ID1 is used to identify a T-CONT1 allocated tothe ONU1, a start time 700 and an end time 900 indicate that the ONU1starts to send data at the 700^(th) byte and ends sending of the data atthe 900^(th) byte, the T-CONT1 is used to carry a data capacity of 200bytes, and the T-CONT1 is used to carry data of the ONU1. In one BWMapmessage in one period, bandwidth authorization may be allocated to thedata of the ONU1 twice in a specified time, and the data transmitted bythe ONU1 may be data of a same service type, or may be data of differentservice types. For example, video data of the ONU1 may be separatelycarried by the T-CONT1 and the T-CONT2, the video data starts to betransmitted at the 100^(th) byte, transmission of the video data stopsat the 300^(th) byte, the video data starts to be transmitted again atthe 700^(th) byte, and transmission of the video data ends at the900^(th) byte.

After such design, bandwidth authorization may be allocated to the videodata of the ONU1 twice in one period in order to transmit the videodata. One transmission period is generally 125 μs. That is, within the125 μs seconds, the video data may be transmitted twice. If one periodis 125 μs, a transmission time corresponding to each T-CONT is 125/6that is approximately 21 μs, that is, a time interval betweentransmitting the video data for a first time and transmitting the videodata for a next time is 63 μs. However, in an existing DBA transmissionmechanism, if the ONU1 transmits the video data only once within 125 μs,a time interval between transmitting the video data for a current timeand transmitting the video data for a next time is 125 μs, and if theONU1 misses this time of data transmission, the ONU1 needs to wait for125 μs to perform transmission for a second time. It can be learnedthat, according to such improvement on a BWMap message format in thisembodiment of this application, not only a service flow transmissioninterval of each ONU can be shortened, but also a transmission delay ofthe ONU is greatly reduced. It can be learned from an experiment that anaverage transmission delay of the ONU can be reduced to within 20 μssuch that a problem that a transmission delay does not satisfy arequirement when a PON system is applied to mobile backhaul is resolved,a data transmission rate and data transmission efficiency are improved,and user satisfaction is improved.

Further, the OLT generates a BWMap message, that may further include afourth allocation identifier (Alloc-ID4) used to identify a T-CONT4allocated to the ONU2, a start time 1000 and an end time 1050 indicatethat the ONU2 starts to send data at the 1000^(th) byte and ends sendingof the data at the 1050^(th) byte, the T-CONT4 is used to carry a datacapacity of 50 bytes, and the T-CONT4 is used to carry data of the ONU2.In such design, in one BWMap message in one period, the ONU2 mayseparately transmit data of different types in a specified time, or maytransmit data of a same service type. For example, video data of theONU2 may be carried by the T-CONT4, the video data starts to betransmitted at the 1000^(th) byte, and transmission of the video dataends at the 1050^(th) byte, or the ONU2 may start to transmit networkaccess data at the 1000^(th) byte, and end transmission of the networkaccess data at the 1050^(th) byte. In such design, for the ONU2 and dataof different service types, a transmission time of to-be-transmitteddata of various service types in the ONU2 is also greatly reduced, adata transmission delay of the ONU2 is greatly reduced, and arequirement that a transmission delay of each ONU in such design iswithin 20 μs is satisfied such that a transmission rate and transmissionefficiency of the data of the various service types are improved, anduser satisfaction is improved.

Corresponding to descriptions in the foregoing embodiment, an allocationperiod corresponding to the BWMap message is shown in FIG. 4 . Theallocation period is described using an example in which each existingperiod is 125 μs, but is not limited to the period. When the allocationperiod is 125 μs, a time corresponding to each T-CONT is 125/6 that isapproximately 21 μs, that is, it takes the T-CONT1 approximately 21 μsto transmit data once. A time interval from transmitting data by theONU1 μsing the T-CONT1 to transmitting data using the T-CONT1 for a nexttime is 21×3 that is 63 μs. Within 125 μs, the T-CONT1 may be used tocarry to-be-sent data of the ONU1 twice. That is, in comparison withother approaches, in one period, a transmission time interval of datatransmission of the ONU is reduced from 125 μs to 63 μs. Therefore,using the design, a calculated average delay of the ONU1 can also bereduced to within 20 μs.

As shown in FIG. 5A and FIG. 5B, alternatively, the BWMap messagegenerated by the OLT may be further in a message format shown in FIG. 5Aand FIG. 5B. A difference from FIG. 4 is that, in the BWMap messageformat shown in FIG. 5A and FIG. 5B, in addition to allocating bandwidthauthorization to the T-CONT1 of the ONU1 twice, the OLT may furtherallocate bandwidth authorization to the ONU2 and the ONU3 or the ONU4once. This BWMap message format may be compatible with a format in whichbandwidth authorization is allocated to the ONU1 twice in FIG. 5A andFIG. 5B, and may also be compatible with a format in which bandwidthauthorization is allocated to another ONU once in an existing BWMapmessage. Details are as follows.

The Alloc-ID1 is used to identify a T-CONT1 allocated to the ONU1, astart time 100 and an end time 300 indicate that the ONU1 starts to senddata at the 100^(th) byte and ends sending of the data at the 300^(th)byte, the T-CONT1 is used to carry a data capacity of 200 bytes, and theT-CONT1 is used to carry data of the ONU1. The Alloc-ID2 is used toidentify a T-CONT2 allocated to the ONU2, a start time 400 and an endtime 500 indicate that the ONU2 starts to send data at the 400^(th) byteand ends sending of the data at the 500^(th) byte, the T-CONT2 is usedto carry a data capacity of 100 bytes, and the T-CONT2 is used to carrydata of the ONU2. The Alloc-ID3 is used to identify a T-CONT3 allocatedto an ONU3, a start time 520 and an end time 600 indicate that the ONU3starts to send data at the 520^(th) byte and ends sending of the data atthe 600^(th) byte, the T-CONT3 is used to carry a data capacity of 80bytes, and the T-CONT3 is used to carry data of the ONU3. The BWMapmessage in this period further includes that the Alloc-ID1 is used toidentify a T-CONT1 allocated to the ONU1, a start time 700 and an endtime 900 indicate that the ONU1 starts to send data at the 700^(th) byteand ends sending of the data at the 900^(th) byte, the T-CONT1 is usedto carry a data capacity of 200 bytes, and the T-CONT1 is used to carrydata of the ONU1. In one BWMap message in one period, bandwidthauthorization may be allocated to the data of the ONU1 twice in aspecified time, and the data transmitted by the ONU1 may be data of asame service type, or may be data of different service types. Forexample, video data of the ONU1 may be separately carried by the T-CONT1and the T-CONT2, the video data starts to be transmitted at the 100^(th)byte, transmission of the video data ends at the 300^(th) byte, thevideo data starts to be transmitted again at the 700^(th) byte, andtransmission of the video data ends at the 900^(th) byte.

After such design, bandwidth authorization may be allocated to the videodata of the ONU1 twice in one period in order to transmit the videodata. One transmission period is generally 125 μs. That is, within the125 μs seconds, the video data may be transmitted twice. If one periodis 125 μs, a transmission time corresponding to each T-CONT is 125/6that is approximately 21 μs, that is, a time interval betweentransmitting the video data for a first time and transmitting the videodata for a next time is 63 μs. However, in an existing DBA transmissionmechanism, if the ONU1 transmits the video data only once within 125 μs,a time interval between transmitting the video data for a current timeand transmitting the video data for a next time is 125 μs, and if theONU1 misses this time of data transmission, the ONU1 needs to wait for125 μs to perform transmission for a second time. It can be learnedthat, according to such improvement on a BWMap message format in thisembodiment of this application, not only a service flow transmissioninterval of each ONU can be shortened, but also a transmission delay ofthe ONU is greatly reduced. It can be learned from an experiment that anaverage transmission delay of the ONU can be reduced to within 20 μssuch that a problem that a transmission delay does not satisfy arequirement when a PON system is applied to mobile backhaul is resolved,a data transmission rate and data transmission efficiency are improved,and user satisfaction is improved.

Further, that the OLT generates a BWMap message may further include anAlloc-ID4 is used to identify a T-CONT4 allocated to an ONU4, a starttime 1000 and an end time 1050 indicate that the ONU4 starts to senddata at the 1000^(th) byte and ends sending of the data at the 1050^(th)byte, the T-CONT4 is used to carry a data capacity of 50 bytes, and theT-CONT4 is used to carry data of the ONU4. In such design, it indicatesthat the BWMap message may allocate bandwidth authorization to the ONU1twice in one period, and after fixed bandwidth authorization isallocated to each ONU, may further be compatible with an existingbandwidth allocation mechanism, and remaining bandwidth is used byanother ONU to which bandwidth authorization is allocated only once,such as start bytes and end bytes of bandwidth authorization shown by anAlloc-ID5, an Alloc-ID6, and an Alloc-ID7. In such design, a bandwidthallocation period of the ONU1 is 125 μs/N, while a bandwidth allocationperiod of the ONU4 is 125 μs. The system is allowed to support thiscase. Therefore, a transmission time of to-be-transmitted data ofvarious service types in each ONU is greatly shortened, a datatransmission delay of the system is greatly reduced, and a requirementthat a transmission delay of each ONU in such design is within 20 μs issatisfied such that a transmission rate and transmission efficiency ofthe data of the various service types are improved, and usersatisfaction is improved.

Corresponding to descriptions in the foregoing embodiment, an allocationperiod corresponding to the BWMap message is shown in FIG. 6 , and theT-CONT1 carries the data of the ONU1. In addition, descriptions ofbandwidth authorization corresponding to the existing DBA allocationmechanism are added, such as the Alloc-ID2, the Alloc-ID3, theAlloc-ID4, and the fifth allocation identifier (Alloc-ID5). Theallocation period is described using an example in which each existingperiod is 125 μs, but is not limited to the period. When the allocationperiod is 125 μs, a time corresponding to each T-CONT is 125/6 that isapproximately 21 μs, that is, it takes the T-CONT1 approximately 21 μsto transmit data once. A time interval from transmitting data by theONU1 μsing the T-CONT1 to transmitting data using the T-CONT1 for a nexttime is 21×3 that is 63 μs. Within 125 μs, the T-CONT1 may be used tocarry bandwidth authorization allocated to the ONU1 twice. That is, incomparison with the other approaches, a bandwidth authorization timeslotof the ONU1 is smaller, and in one period, a transmission time intervalof each time of data transmission of the ONU is reduced from 125 μs to63 μs. Therefore, using the design, a calculated average delay of theONU1 can also be reduced to within 20 μs.

FIG. 7A and FIG. 7B show another BWMap message format, the messageformat is basically the same as the foregoing two BWMap message formats,and a relative location of each field in the message format is also thesame as a relative location of each field in the foregoing two BWMapmessage.

FIG. 7A and FIG. 7B show a format of a downstream frame n that isdelivered by the OLT to the ONU, and the downstream frame includes aframe header and a frame payload. An upstream BWMap (US BWMap) messageformat is located at a frame header part of the downstream frame n, anddetails are as follows.

The Alloc-ID1 is used to identify a T-CONT1 allocated to the ONU1, astart time 100 and an end time 300 indicate that the ONU1 starts to senddata at the 100^(th) byte and ends sending of the data at the 300^(th)byte, the T-CONT1 is used to carry a data capacity of 200 bytes, and theT-CONT1 is used to carry data of the ONU1. The Alloc-ID2 is used toidentify a T-CONT2 allocated to the ONU2, a start time 400 and an endtime 500 indicate that the ONU2 starts to send data at the 400^(th) byteand ends sending of the data at the 500^(th) byte, the T-CONT2 is usedto carry a data capacity of 100 bytes, and the T-CONT2 is used to carrydata of the ONU2. The Alloc-ID3 is used to identify a T-CONT3 allocatedto an ONU3, a start time 520 and an end time 600 indicate that the ONU3starts to send data at the 520^(th) byte and ends sending of the data atthe 600^(th) byte, the T-CONT3 is used to carry a data capacity of 80bytes, and the T-CONT3 is used to carry data of the ONU3. Implementationof this BWMap message is different from implementation of existing BWMapmessage. The BWMap message in this period further includes that theAlloc-ID1 is used to identify a T-CONT1 allocated to the ONU1, a starttime 700 and an end time 900 indicate that the ONU1 starts to send dataat the 700^(th) byte and ends sending of the data at the 900^(th) byte,the T-CONT1 is used to carry a data capacity of 200 bytes, and theT-CONT1 is used to carry data of the ONU1. In one BWMap message in oneperiod, bandwidth authorization may be allocated to the data of the ONU1twice in a specified time, and the data transmitted by the ONU1 may bedata of a same service type, or may be data of different service types.For example, video data of the ONU1 may be separately carried by theT-CONT1 and the T-CONT2, the video data starts to be transmitted at the100^(th) byte, transmission of the video data ends at the 300^(th) byte,the video data starts to be transmitted again at the 700^(th) byte, andtransmission of the video data ends at the 900^(th) byte.

After such design, bandwidth authorization may be allocated to the videodata of the ONU1 twice in one period in order to transmit the videodata. One transmission period is generally 125 μs. That is, within the125 μs seconds, the video data may be transmitted twice. If one periodis 125 μs, a transmission time corresponding to each T-CONT is 125/6that is approximately 21 μs, that is, a time interval betweentransmitting the video data for a first time and transmitting the videodata for a next time is 63 μs. However, in an existing DBA transmissionmechanism, if the ONU1 transmits the video data only once within 125 μs,a time interval between transmitting the video data for a current timeand transmitting the video data for a next time is 125 μs, and if theONU1 misses this time of data transmission, the ONU1 needs to wait for125 μs to perform transmission for a second time. It can be learnedthat, according to such improvement on a BWMap message format in thisembodiment of this application, not only a service flow transmissioninterval of each ONU can be shortened, but also a transmission delay ofthe ONU is greatly reduced. It can be learned from an experiment that anaverage transmission delay of the ONU can be reduced to within 20 μssuch that a problem that a transmission delay does not satisfy arequirement when a PON system is applied to mobile backhaul is resolved,a data transmission rate and data transmission efficiency are improved,and user satisfaction is improved.

Further, that the OLT generates a BWMap message may further include anAlloc-ID4 is used to identify a T-CONT4 allocated to the ONU2, a starttime 1000 and an end time 1050 indicate that the ONU2 starts to senddata at the 1000^(th) byte and ends sending of the data at the 1050^(th)byte, the T-CONT4 is used to carry a data capacity of 50 bytes, and theT-CONT4 is used to carry data of the ONU2. In such design, in one BWMapmessage in one period, the ONU2 may separately transmit data ofdifferent types in a specified time, or may transmit data of a sameservice type. For example, video data of the ONU2 may be carried by theT-CONT4, the video data starts to be transmitted at the 1000^(th) byte,and transmission of the video data ends at the 1050^(th) byte, or theONU2 may start to transmit network access data at the 1000^(th) byte,and end transmission of the network access data at the 1050^(th) byte.In such design, for the ONU2 and data of different service types, atransmission time of to-be-transmitted data of various service types inthe ONU2 is also greatly reduced, a data transmission delay of the ONU2is greatly reduced, and a requirement that a transmission delay of eachONU in such design is within 20 μs is satisfied such that a transmissionrate and transmission efficiency of the data of the various servicetypes are improved, and user satisfaction is improved.

According to the foregoing descriptions with reference to theaccompanying drawings, in two successive times of bandwidthauthorization, the Alloc-ID1 indicates a T-CONT allocated to the ONU1.In a next period, a location of the Alloc-ID1 is also relatively fixed.Therefore, according to a DBA mechanism of an improved BWMap messageformat, a transmission delay between the ONU and the OLT can be reduced,and transmission efficiency and a transmission rate are improved.

Step S206: The OLT sends the BWMap message to each ONU.

Further, the OLT broadcasts the BWMap message to each ONU.

Step S208: The ONU1 receives the BWMap message returned by the OLT.

Further, the method may further include the following steps (not shown).

Step S210: The ONU1 obtains, according to an Alloc-ID of the ONU1, afirst time and a second time corresponding to the ONU1.

Step S212: Transmit first data according to the obtained first time, andtransmit second data according to the second time.

Further, the OLT pre-allocates an Alloc-ID to each ONU using amanagement configuration message, and the ONU receives and saves theAlloc-ID of the ONU. When the ONU1 receives the BWMap message sent bythe OLT by means of broadcasting, each ONU obtains a T-CONT of the ONUaccording to an Alloc-ID of the ONU, and further obtains bandwidthauthorization of the T-CONT, that is, obtains a first time correspondingto the T-CONT. If the ONU learns, by searching for an Alloc-ID, thatbandwidth authorization is allocated to the ONU at least twice in oneBWMap message in one period, the ONU transmits data separately accordingto a bandwidth authorization time in the message, that is, transmits thefirst data according to the obtained first time, and transmits thesecond data according to the second time. The first time corresponds toa byte at which data carried by the T-CONT starts to be sent and a byteat which sending of the data ends, and the second time corresponds to abyte at which data carried by the T-CONT starts to be sent and a byte atwhich sending of the data ends. The first time and the second time areallocated in ascending order.

After such design, bandwidth authorization may be allocated to the videodata of the ONU1 twice in one period in order to transmit the videodata. One transmission period is generally 125 μs. That is, within the125 μs seconds, the video data may be transmitted twice. If one periodis 125 μs, a transmission time corresponding to each T-CONT is 125/6that is approximately 21 μs, that is, a time interval betweentransmitting the video data for a first time and transmitting the videodata for a next time is 63 μs. However, in an existing DBA transmissionmechanism, if the ONU1 transmits the video data only once within 125 μs,a time interval between transmitting the video data for a current timeand transmitting the video data for a next time is 125 μs, and if theONU1 misses this time of data transmission, the ONU1 needs to wait for125 μs to perform transmission for a second time. It can be learnedthat, according to such improvement on a BWMap message format in thisembodiment of this application, not only a service flow transmissioninterval of each ONU can be shortened, but also a transmission delay ofthe ONU is greatly reduced. It can be learned from an experiment that anaverage transmission delay of the ONU can be reduced to within 20 μssuch that a problem that a transmission delay does not satisfy arequirement when a PON system is applied to mobile backhaul is resolved,a data transmission rate and data transmission efficiency are improved,and user satisfaction is improved.

An embodiment of the present disclosure further provides an OLT. Asshown in FIG. 8 , the OLT includes a transceiver 800 configured toreceive a bandwidth request sent by each ONU, where the ONU includes afirst ONU1, and send a BWMap message to each ONU, and a processor 802configured to generate the BWMap message according to bandwidthrequested by the ONU and bandwidth configured by the ONU, where theBWMap message includes an Alloc-ID1, a first time corresponding to theAlloc-ID1, an Alloc-ID2, and a second time corresponding to theAlloc-ID2, and both the Alloc-ID1 and the Alloc-ID2 are allocated to theONU1 for use.

Further, the BWMap message further includes an Alloc-ID3 and a thirdtime corresponding to the Alloc-ID3, the Alloc-ID3 is used to identify asecond ONU2, and the third time is used to be allocated to the ONU2 foruse.

Further, the first time includes a first start time start time 1 and afirst end time end time 1, the second time includes a second start timestart time 2 and a second end time end time 2, the start time 1 is usedto indicate a byte at which the ONU1 starts to transmit a first datastream, the end time 1 is used to indicate a byte at which the ONU1 endstransmission of the first data stream, the start time 2 is used toindicate a byte at which the ONU1 starts to transmit a second datastream, the second end time end time 2 is used to indicate a byte atwhich the ONU1 ends transmission of the second data stream, and thefirst data stream and the second data stream carry service flows of asame type, or the first data stream and the second data stream carryservice flows of different types.

Further, a location of the Alloc-ID1 relative to the Alloc-ID2 is fixedin a BWMap message in each period.

For the BWMap message generated by the OLT, refer to FIG. 2 to FIG. 7Band corresponding descriptions. Details are not described herein again.

For a location of the foregoing OLT in a PON system architecture, referto the OLT shown in FIG. 1 . The foregoing transceiver 800 may be theoptical transceiver component 200 of the OLT 110 in the systemarchitecture, or the transceiver 800 is located in the opticaltransceiver component 200 of the OLT in the system architecture.

According to improvement on a format of the BWMap message generated bythe OLT in this embodiment of this application, not only a service flowtransmission interval of each ONU can be shortened, but also atransmission delay of the ONU is greatly reduced. It can be learned froman experiment that an average transmission delay of the ONU can bereduced to within 20 μs such that a problem that a transmission delaydoes not satisfy a requirement when a PON system is applied to mobilebackhaul is resolved, a data transmission rate and data transmissionefficiency are improved, and user satisfaction is improved.

With reference to system architecture diagrams in FIG. 8 and FIG. 1 ,the OLT in FIG. 1 further includes the processor 802 shown in FIG. 8 ,and the processor 800 is not shown in FIG. 1 . The processor 800 in FIG.8 may be a media access controller (MAC) or another microprocessor.

An embodiment of the present disclosure further provides an ONU. Asshown in FIG. 9 , the ONU includes a transmitter 900 configured to senda bandwidth request to an OLT, and a receiver 902 configured to receivea BWMap message returned by the OLT, where the BWMap message includes anAlloc-ID1, a first time corresponding to the Alloc-ID1, an Alloc-ID2,and a second time corresponding to the Alloc-ID2, and both the Alloc-ID1and the Alloc-ID2 are allocated to the first ONU1.

The ONU further includes a processor 904 configured to obtain, accordingto an Alloc-ID of the ONU1, a first time and a second time correspondingto the ONU1, and instruct the transmitter to transmit data in the firsttime and the second time.

The transmitter 900 is further configured to transmit first dataaccording to the obtained first time, and transmit second data accordingto the second time.

The BWMap message further includes an Alloc-ID3 and a third timecorresponding to the Alloc-ID3, the Alloc-ID3 is used to identify asecond ONU2, and the third time is used to be allocated to the ONU2 foruse.

Further, the first time includes a first start time start time 1 and afirst end time end time 1, the second time includes a second start timestart time 2 and a second end time end time 2, the start time 1 is usedto indicate a byte at which the ONU1 starts to transmit a first datastream, the end time 1 is used to indicate a byte at which the ONU1 endstransmission of the first data stream, the start time 2 is used toindicate a byte at which the ONU1 starts to transmit a second datastream, the second end time end time 2 is used to indicate a byte atwhich the ONU1 ends transmission of the second data stream, and thefirst data stream and the second data stream carry service flows of asame type, or the first data stream and the second data stream carryservice flows of different types.

Further, a location of the Alloc-ID1 relative to the Alloc-ID2 is fixedin a BWMap message in each period.

For a structure of the BWMap message received by the foregoing ONU,refer to FIG. 2 to FIG. 7B and corresponding descriptions. Details arenot described herein again.

According to improvement on a format of the BWMap message received bythe ONU in this embodiment of this application, not only a service flowtransmission interval of each ONU can be shortened, but also atransmission delay of the ONU is greatly reduced. It can be learned froman experiment that an average transmission delay of the ONU can bereduced to within 20 μs such that a problem that a transmission delaydoes not satisfy a requirement when a PON system is applied to mobilebackhaul is resolved, a data transmission rate and data transmissionefficiency are improved, and user satisfaction is improved.

With reference to a system architecture diagram in FIG. 1 , the opticaltransceiver component 300 in FIG. 1 may include the transmitter 900 andthe receiver 902 in FIG. 9 . In addition, the transmitter 900 and thereceiver 902 may be assembled into a component, such as an opticalmodule, or may be disposed separately.

The processor 904 is not shown for the ONU 120 in FIG. 1 , but the ONUalso includes the processor 904. The processor 904 in FIG. 9 may be aMAC or another microprocessor.

The PON system 100 shown in FIG. 1 includes an OLT 110 and an ONU 120,and the OLT 110 is connected to the ONU 120 using an ODN. For astructure of the OLT 110, refer to descriptions of a specific structureof the foregoing OLT, for a specific structure of the ONU, refer todescriptions of a specific structure of the foregoing ONU, and forfunctions performed by the OLT and the ONU, refer to descriptions of theforegoing embodiments respectively. Details are not described hereinagain.

According to improvement on a format of the BWMap message generated bythe OLT in this embodiment of this application, not only a service flowtransmission interval of each ONU can be shortened, but also atransmission delay of the ONU is greatly reduced. It can be learned froman experiment that an average transmission delay of the ONU can bereduced to within 20 μs such that a problem that a transmission delaydoes not satisfy a requirement when a PON system is applied to mobilebackhaul is resolved, a data transmission rate and data transmissionefficiency are improved, and user satisfaction is improved.

As shown in FIG. 10 , an embodiment of the present disclosure furtherprovides a data communications device. As shown in FIG. 10 , the datacommunications device includes a processor, a memory, and a bus system.The processor and the memory are connected using the bus system, thememory is configured to store an instruction, and the processor isconfigured to execute the instruction stored in the memory.

When the data communications device is an OLT, the processor isconfigured to receive a bandwidth request sent by each ONU, where theONU includes a first ONU1, generate a BWMap message according tobandwidth requested by the ONU and bandwidth configured for the ONU,where the BWMap message includes a first allocation identifierAlloc-ID1, a first time corresponding to the Alloc-ID1, a secondallocation identifier Alloc-ID2, and a second time corresponding to theAlloc-ID2, and both the Alloc-ID1 and the Alloc-ID2 are allocated to theONU1 for use, and send the BWMap message to each ONU.

In another embodiment, when the data communications device is an ONU,the processor may be configured to send a BWMap request to an OLT torequest the OLT to allocate bandwidth, and receive a BWMap messagereturned by the OLT, where the BWMap message includes an Alloc-ID1, afirst time corresponding to the Alloc-ID1, an Alloc-ID2, and a secondtime corresponding to the Alloc-ID2, and both the Alloc-ID1 and theAlloc-ID2 are allocated to the first ONU1 for use.

The sequence numbers of the foregoing embodiments of this applicationare merely for illustrative purposes, but are not intended to indicatepriorities of the embodiments.

According to a format of the BWMap message in this embodiment of thisapplication, not only a service flow transmission interval of each ONUcan be shortened, but also a transmission delay of the ONU is greatlyreduced. It can be learned from an experiment that an averagetransmission delay of the ONU can be reduced to within 20 μs such that aproblem that a transmission delay does not satisfy a requirement when aPON system is applied to mobile backhaul is resolved, a datatransmission rate and data transmission efficiency are improved, anduser satisfaction is improved.

A person of ordinary skill in the art may understand that all or some ofthe steps of the embodiments may be implemented by hardware or a programinstructing related hardware. The program may be stored in acomputer-readable storage medium. The storage medium may be a read-onlymemory, a magnetic disk, an optical disc, or the like.

The foregoing descriptions are merely specific embodiments of thisapplication, but are not intended to limit this application. Anymodification, equivalent replacement, or improvement made withoutdeparting from the spirit and principle of this application should fallwithin the protection scope of this application.

What is claimed is:
 1. A bandwidth allocation method comprising:generating a bandwidth map (BWMap) message according to bandwidthconfigured for a plurality of optical network units (ONUs), wherein theBWMap message comprises first allocation identifiers, wherein each firstallocation identifier corresponds to a different time slot in a grantperiod corresponding to the BWMap message, wherein the grant period is125 microseconds (μs), and wherein the first allocation identifiers areallocated to a first ONU of the ONUs; and sending the BWMap message toeach of the ONUs.
 2. The method of claim 1, wherein the BWMap messagefurther comprises at least two second allocation identifiers, whereineach second allocation identifier corresponds to a different time slot,wherein the second allocation identifiers identify a second ONU of theONUs.
 3. The method of claim 2, wherein second intervals of adjacentsecond allocation identifiers are the same.
 4. The method of claim 1,wherein the different time slots comprise a first time slot and a secondtime slot, wherein the first time slot comprises a first start time anda first end time, wherein the second time slot comprises a second starttime and a second end time, wherein the first start time indicates afirst byte at which the first ONU starts to transmit a first datastream, wherein the first end time indicates a second byte at which thefirst ONU ends transmission of the first data stream, wherein the secondstart time indicates a third byte at which the first ONU starts totransmit a second data stream, wherein the second end time indicates afourth byte at which the first ONU ends transmission of the second datastream, and wherein the first data stream and the second data streamcarry service flows of a same type or service flows of different types.5. The method of claim 1, wherein adjacent first allocation identifiersare not contiguous, and wherein intervals of the adjacent allocationidentifiers are the same.
 6. The method of claim 1, wherein the BWMapmessage comprises two first allocation identifiers and a thirdallocation identifier, the third allocation identifier is allocated to athird ONU of the ONUs, and the third allocation identifier is locatedbetween the two first allocation identifiers.
 7. A bandwidth allocationmethod comprising receiving a bandwidth map (BWMap) message from anoptical line terminal (OLT), wherein the BWMap message comprises firstallocation identifiers, wherein each first allocation identifiercorresponds to a different time slot in a grant period corresponding tothe BWMap message, and wherein the grant period is 125 microseconds(μs).
 8. The method of claim 7, further comprising: obtaining, accordingto at least two allocation identifiers of a first ONU, at least twofirst times corresponding to the first ONU; transmitting first dataaccording to one of the at least two first times; and transmittingsecond data according to another one of the at least two first times. 9.The method of claim 7, wherein adjacent first allocation identifiers arenot contiguous, and wherein intervals of the adjacent allocationidentifiers are the same.
 10. The method of claim 7, wherein thedifferent time slots comprise a first time slot and a second time slot,wherein the first time slot comprises a first start time and a first endtime, wherein the second time slot comprises a second start time and asecond end time, wherein the first start time indicates a first byte atwhich the first ONU starts to transmit a first data stream, wherein thefirst end time indicates a second byte at which the first ONU endstransmission of the first data stream, wherein the second start timeindicates a third byte at which the first ONU starts to transmit asecond data stream, wherein the second end time indicates a fourth byteat which the first ONU ends transmission of the second data stream, andwherein the first data stream and the second data stream carry serviceflows of a same type or service flows of different types.
 11. The methodof claim 7, wherein the BWMap message further comprises at least twosecond allocation identifiers, wherein each second allocation identifiercorresponds to a different time slot, wherein the second allocationidentifiers identify a second ONU, and wherein a second interval ofadjacent second allocation identifiers is the same.
 12. The method ofclaim 7, wherein the BWMap message comprises two first allocationidentifiers and a third allocation identifier, the third allocationidentifier is allocated to a third ONU, and the third allocationidentifier is located between the two first allocation identifiers. 13.An optical line terminal (OLT) comprising: a processor configured togenerate a bandwidth map (BWMap) message according to bandwidthconfigured for a plurality of optical network units (ONUs), wherein theBWMap message comprises first allocation identifiers, wherein each firstallocation identifier corresponds to a different time slot in a grantperiod corresponding to the BWMap message, wherein the grant period is125 μs, and wherein the first allocation identifiers are allocated to afirst ONU of the ONUs; and a transceiver coupled to the processor andconfigured to send the BWMap message to the ONUs.
 14. The OLT of claim13, wherein the BWMap message further comprises at least two secondallocation identifiers, wherein each second allocation identifiercorresponds to a different time slot, wherein the second allocationidentifiers identify a second ONU of the ONUs, and wherein a secondinterval of adjacent second allocation identifiers is the same.
 15. TheOLT of claim 13, wherein the different time slots comprise a first timeslot and a second time slot, wherein the first time slot comprises afirst start time and a first end time, wherein the second time slotcomprises a second start time and a second end time, wherein the firststart time indicates a first byte at which the first ONU starts totransmit a first data stream, wherein the first end time indicates asecond byte at which the first ONU ends transmission of the first datastream, wherein the second start time indicates a third byte at whichthe first ONU starts to transmit a second data stream, wherein thesecond end time indicates a fourth byte at which the first ONU endstransmission of the second data stream, and wherein the first datastream and the second data stream carry service flows of a same type orservice flows of different types.
 16. The OLT of claim 13, wherein theBWMap message comprises two first allocation identifiers and a thirdallocation identifier, the third allocation identifier is allocated to athird ONU of the ONUs, and the third allocation identifier is locatedbetween the two first allocation identifiers.
 17. An optical networkunit (ONU) comprising a receiver configured to receive a bandwidth map(BWMap) message from an optical line terminal (OLT), wherein the BWMapmessage comprises first allocation identifiers, wherein each firstallocation identifier corresponds to a different time slot in a grantperiod corresponding to the BWMap message, and wherein the grant periodis 125 microseconds (μs).
 18. The ONU of claim 17, further comprising aprocessor coupled to a transmitter and the receiver, wherein theprocessor is configured to: obtain, according to at least two allocationidentifiers of the ONU, at least two time slots corresponding to theONU; and instruct the transmitter to transmit data in the time slots,and wherein the transmitter is configured to: transmit first dataaccording to one of the time slots; and transmit second data accordingto another one of the time slots.
 19. The ONU of claim 17, wherein theBWMap message comprises two first allocation identifiers and a thirdallocation identifier, the third allocation identifier is allocated to athird ONU, and the third allocation identifier is located between thetwo first allocation identifiers.
 20. The ONU of claim 17, wherein thedifferent time slots comprise a first time slot and a second time slot,wherein the first time slot comprises a first start time and a first endtime, wherein the second time slot comprises a second start time and asecond end time, wherein the first start time indicates a first byte atwhich the ONU starts to transmit a first data stream, wherein the firstend time indicates a second byte at which the ONU ends transmission ofthe first data stream, wherein the second start time indicates a thirdbyte at which the ONU starts to transmit a second data stream, whereinthe second end time indicates a fourth byte at which the ONU endstransmission of the second data stream, and wherein the first datastream and the second data stream carry service flows of a same type orservice flows of different types.
 21. A data stream transmitting methodcomprising: receiving, by an optical network unit (ONU), a bandwidth map(BWMap) message from an optical line terminal (OLT), wherein the BWMapmessage includes a grant period for data transmission, and the grantperiod is 125 microseconds (μs); sending, by the ONU, a data stream ofthe ONU to the OLT in a first time slot of the grant period; andsending, by the ONU, the data stream of the ONU to the OLT in a secondtime slot of the grant period, wherein at least one time slot is spacedbetween the first time slot and the second time slot.
 22. The method ofclaim 21, wherein the first time slot comprises a first start time and afirst end time, wherein the first start time indicates a first byte atwhich the ONU starts to transmit the data stream, wherein the first endtime indicates a second byte at which the ONU ends transmission of thedata stream.
 23. The method of claim 21, wherein the BWMap messagecomprises a first allocation identifier of the ONU corresponds to thefirst time slot of the grant period, and a second allocation identifierof the ONU corresponds to the second time slot of the grant period. 24.An optical network unit (ONU) comprising: a transceiver configured toreceive a bandwidth map (BWMap) message from an optical line terminal(OLT), wherein the BWMap message includes a grant period for datatransmission, and the grant period is 125 microseconds (μs); thetransceiver is configured to send a data stream of the ONU to the OLT ina first time slot of the grant period; and to send the data stream ofthe ONU to the OLT in a second time slot of the grant period, wherein atleast one time slot is spaced between the first time slot and the secondtime slot.
 25. The ONU of claim 24, wherein the first time slotcomprises a first start time and a first end time, wherein the firststart time indicates a first byte at which the ONU starts to transmitthe data stream, wherein the first end time indicates a second byte atwhich the ONU ends transmission of the data stream.
 26. The ONU of claim24, wherein the BWMap message comprises a first allocation identifier ofthe ONU corresponds to the first time slot of the grant period, and asecond allocation identifier of the ONU corresponds to the second timeslot of the grant period.